1. Field of the Invention
This invention relates to accelerating the cure of epoxy resins.
2. Discussion of Prior Publications
Epoxy resins constitute a broad class of polymeric materials having a wide range of physical characteristics. The resins are characterized by epoxide groups which are cured by reaction with catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties.
U.S. Pat. No. 4,518,749 to H. G. Waddill teaches an epoxy resin composition comprising a polyepoxide and a curing amount of a bis(hydrogen maleate) derivative of a polyoxypropylenediamine. Example 3 teaches that tris(dimethylaminomethyl)phenol is an accelerator for the curing of an epoxy resin. Handbook of Epoxy Resins, H. Lee and K. Neville, p. 7-2 states that in curing epoxy resins with amines, that tris(dimethylaminomethyl)phenol is superior to phenol.
U.S. Pat. No. 3,875,072 to H. G. Waddill teaches a composition which is synergistic for accelerating the curing of a polyglycidyl ether of a polyhydric phenol cured with a polyoxyalkylenepolyamine. The composition comprises piperazine and an alkanolamine in a weight ratio of 1:8 to 1:1.
U.S. Pat. No. 4,195,153 to H. G. Waddill teaches an epoxy resin curing accelerator comprising a mixture of N-aminoethylpiperazine (AEP) and triethanolamine (TEA).
U.S. Pat. No. 4,189,546 to H. G. Waddill teaches an epoxy resin curing accelerator comprising a mixture of piperazine, N-aminoethylpiperazine (AEP) and triethanolamine (TEA). The mixture is synergistic for curing an epoxy resin with an amine at ambient or elevated temperature.
U.S. Pat. No. 3,236,895 to J. M. Lee and J. C. Winfrey and U.S. Pat. No. 3,462,393 to Legler are pioneer patents. They describe a series of amine compounds which are solids or liquids and have utility particularly in curing epoxy resins. The amine compounds have the general formula: ##STR1## wherein R's are selectively defined as hydrogen, alkyl radicals and alkylene oxide radicals and x and m are defined integers.
U.S. Pat. No. 3,864,358 to D. Porret and J. Habermeier describes epoxy-acrylic acid esters obtained when 3-(acryloyl-oxyalkyl)-hydantoins are glycidylated. Both 2,4,6-tris(dimethylaminoethyl)phenol and N-(2-aminoethyl)piperazine are mentioned as epoxy resin curing agents. The compound 2,4,6-tris(dimethylaminoethyl)phenol is taught as an accelerator for the curing of epoxy resins. In contrast, these compounds are used in combination, in small amounts as an accelerator in the instant invention.
U.S. Pat. No. 4,284,547 to M. M. Bagga teaches diglycidyl ethers of di-secondary alcohols as epoxy resins. Both 2,4,6-tris(dimethylaminoethyl)phenol and N-(2-aminoethyl)piperazine are mentioned as curing agents for epoxy resins. Accelerators include 2,4,6-tris(dimethylaminomethyl)phenol.